Impact Strength and Toughness of Fiber Composite Materials

The drop weight impact energy for beam specimens has been studied using various unidirectional and cross-ply glass fiber laminates. The strength and impact energy of these laminates are strain rate sensitive. The orientation of the lamination planes with respect to the impact load (perpendicular or parallel) is important and determines the failure mode as well as the impact energy. Cross-ply laminates, although weaker than unidirectional laminates, provide the same impact energy absorption in flexure since the dominant failure mode is delamination between layers. Failure models are described to account for the differences in impact energy absorbed for the various composite structures which were tested.